This paper is aimed to study the operation mechanism of Stirling pulse tube refrigerators (PTRs) by tracing working gas elements characteristics at the cold end of the system using both Eulerian and Eulerian-Lagrangian (E-L) methods. The main objective of the investigations is to demonstrate non-symmetry effects in the pulse tube section of the system. Elemental cyclic-enthalpy transfer of simple (S), double-inlet (DI) and multi-mesh regenerator (MM) PTRs are also investigated to demonstrate the effects of DI and MM systems on the refrigeration mechanism of PTRs. It is shown that the elemental cyclic-enthalpy transfer of SPTR is less than those of DIPTR, MMPTR and MMDIPTR, though it's elemental cyclic-temperature reduction is more than the others; because, the mass flow rate upon cold end of the SPTR is less than the others. Regarding the reduction of losses in DIPTR and MMPTR, their cold end mean pressure and density increase which consequently lead the cold end mass flow rate and cyclic-enthalpy transfer to increases. Increase in enthalpy transfer of MM-PTR, MM-DIPTR and DIPTR consequently improves their cooling performance.